Sixty percent of Tabasco State in southern Mexico was covered in original vegetation 30 years ago, however, activities related to clearing areas for cattle ranching, agriculture and forestry, diminished forest cover to less than 10%. Balancan is a municipality located on the border with Guatemala and the North of Chiapas where we found clearly different land uses. In the present study, we examined land use and its affect on the presence and persistence of black howler monkey (Alouatta pigra) populations. During October 2005 – April 2006, we analyzed the group size, population structure and ecological density (individuals/ha) in Balancán municipality (5,414 ha), which included forest fragments within 200 m of each other termed “clusters” (n=26) by SIG’s analyses. We classified habitat as continuous, isolated by temporal and permanent matrix agriculture, cattle ranches or commercially forested. Our results showed a density of 2 individuals/ha, the sex-ratio (male to female) for A. pigra troops was 1:1 (adult), 1:1.2 (young), 1:0.8 (infant) and the ratio of immature to adult females was 1:1. Average group size was 5.0 ± 2.1 individuals per troop, including seven solitary individuals also registered. The density of howlers was very low (0.05 individuals/ha) and the sex ratios were altered in permanent matrix agriculture and cattle ranching in comparison with A. pigra populations from Belize in a better-preserved habitat. Our current data suggest that land uses by humans could be affecting howler populations. This could be related to effects on forest structure and food abundance inside of these fragments. Financial support by Division de Posgrado and Departamento de Biodiversidad y Ecologia Animal (INECOL), Xalapa, Veracruz, Mexico.